fs/fs_parser.c

   1 /* Filesystem parameter parser.
   2  *
   3  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/export.h>
  13 #include <linux/fs_context.h>
  14 #include <linux/fs_parser.h>
  15 #include <linux/slab.h>
  16 #include <linux/security.h>
  17 #include <linux/namei.h>
  18 #include "internal.h"
  19
  20 static const struct constant_table bool_names[] = {
  21         { "0",          false },
  22         { "1",          true },
  23         { "false",      false },
  24         { "no",         false },
  25         { "true",       true },
  26         { "yes",        true },
  27 };
  28
  29 /**
  30  * lookup_constant - Look up a constant by name in an ordered table
  31  * @tbl: The table of constants to search.
  32  * @tbl_size: The size of the table.
  33  * @name: The name to look up.
  34  * @not_found: The value to return if the name is not found.
  35  */
  36 int __lookup_constant(const struct constant_table *tbl, size_t tbl_size,
  37                       const char *name, int not_found)
  38 {
  39         unsigned int i;
  40
  41         for (i = 0; i < tbl_size; i++)
  42                 if (strcmp(name, tbl[i].name) == 0)
  43                         return tbl[i].value;
  44
  45         return not_found;
  46 }
  47 EXPORT_SYMBOL(__lookup_constant);
  48
  49 static const struct fs_parameter_spec *fs_lookup_key(
  50         const struct fs_parameter_description *desc,
  51         const char *name)
  52 {
  53         const struct fs_parameter_spec *p;
  54
  55         if (!desc->specs)
  56                 return NULL;
  57
  58         for (p = desc->specs; p->name; p++)
  59                 if (strcmp(p->name, name) == 0)
  60                         return p;
  61
  62         return NULL;
  63 }
  64
  65 /*
  66  * fs_parse - Parse a filesystem configuration parameter
  67  * @fc: The filesystem context to log errors through.
  68  * @desc: The parameter description to use.
  69  * @param: The parameter.
  70  * @result: Where to place the result of the parse
  71  *
  72  * Parse a filesystem configuration parameter and attempt a conversion for a
  73  * simple parameter for which this is requested.  If successful, the determined
  74  * parameter ID is placed into @result->key, the desired type is indicated in
  75  * @result->t and any converted value is placed into an appropriate member of
  76  * the union in @result.
  77  *
  78  * The function returns the parameter number if the parameter was matched,
  79  * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
  80  * unknown parameters are okay and -EINVAL if there was a conversion issue or
  81  * the parameter wasn't recognised and unknowns aren't okay.
  82  */
  83 int fs_parse(struct fs_context *fc,
  84              const struct fs_parameter_description *desc,
  85              struct fs_parameter *param,
  86              struct fs_parse_result *result)
  87 {
  88         const struct fs_parameter_spec *p;
  89         const struct fs_parameter_enum *e;
  90         int ret = -ENOPARAM, b;
  91
  92         result->has_value = !!param->string;
  93         result->negated = false;
  94         result->uint_64 = 0;
  95
  96         p = fs_lookup_key(desc, param->key);
  97         if (!p) {
  98                 /* If we didn't find something that looks like "noxxx", see if
  99                  * "xxx" takes the "no"-form negative - but only if there
 100                  * wasn't an value.
 101                  */
 102                 if (result->has_value)
 103                         goto unknown_parameter;
 104                 if (param->key[0] != 'n' || param->key[1] != 'o' || !param->key[2])
 105                         goto unknown_parameter;
 106
 107                 p = fs_lookup_key(desc, param->key + 2);
 108                 if (!p)
 109                         goto unknown_parameter;
 110                 if (!(p->flags & fs_param_neg_with_no))
 111                         goto unknown_parameter;
 112                 result->boolean = false;
 113                 result->negated = true;
 114         }
 115
 116         if (p->flags & fs_param_deprecated)
 117                 warnf(fc, "%s: Deprecated parameter '%s'",
 118                       desc->name, param->key);
 119
 120         if (result->negated)
 121                 goto okay;
 122
 123         /* Certain parameter types only take a string and convert it. */
 124         switch (p->type) {
 125         case __fs_param_wasnt_defined:
 126                 return -EINVAL;
 127         case fs_param_is_u32:
 128         case fs_param_is_u32_octal:
 129         case fs_param_is_u32_hex:
 130         case fs_param_is_s32:
 131         case fs_param_is_u64:
 132         case fs_param_is_enum:
 133         case fs_param_is_string:
 134                 if (param->type != fs_value_is_string)
 135                         goto bad_value;
 136                 if (!result->has_value) {
 137                         if (p->flags & fs_param_v_optional)
 138                                 goto okay;
 139                         goto bad_value;
 140                 }
 141                 /* Fall through */
 142         default:
 143                 break;
 144         }
 145
 146         /* Try to turn the type we were given into the type desired by the
 147          * parameter and give an error if we can't.
 148          */
 149         switch (p->type) {
 150         case fs_param_is_flag:
 151                 if (param->type != fs_value_is_flag &&
 152                     (param->type != fs_value_is_string || result->has_value))
 153                         return invalf(fc, "%s: Unexpected value for '%s'",
 154                                       desc->name, param->key);
 155                 result->boolean = true;
 156                 goto okay;
 157
 158         case fs_param_is_bool:
 159                 switch (param->type) {
 160                 case fs_value_is_flag:
 161                         result->boolean = true;
 162                         goto okay;
 163                 case fs_value_is_string:
 164                         if (param->size == 0) {
 165                                 result->boolean = true;
 166                                 goto okay;
 167                         }
 168                         b = lookup_constant(bool_names, param->string, -1);
 169                         if (b == -1)
 170                                 goto bad_value;
 171                         result->boolean = b;
 172                         goto okay;
 173                 default:
 174                         goto bad_value;
 175                 }
 176
 177         case fs_param_is_u32:
 178                 ret = kstrtouint(param->string, 0, &result->uint_32);
 179                 goto maybe_okay;
 180         case fs_param_is_u32_octal:
 181                 ret = kstrtouint(param->string, 8, &result->uint_32);
 182                 goto maybe_okay;
 183         case fs_param_is_u32_hex:
 184                 ret = kstrtouint(param->string, 16, &result->uint_32);
 185                 goto maybe_okay;
 186         case fs_param_is_s32:
 187                 ret = kstrtoint(param->string, 0, &result->int_32);
 188                 goto maybe_okay;
 189         case fs_param_is_u64:
 190                 ret = kstrtoull(param->string, 0, &result->uint_64);
 191                 goto maybe_okay;
 192
 193         case fs_param_is_enum:
 194                 for (e = desc->enums; e->name[0]; e++) {
 195                         if (e->opt == p->opt &&
 196                             strcmp(e->name, param->string) == 0) {
 197                                 result->uint_32 = e->value;
 198                                 goto okay;
 199                         }
 200                 }
 201                 goto bad_value;
 202
 203         case fs_param_is_string:
 204                 goto okay;
 205         case fs_param_is_blob:
 206                 if (param->type != fs_value_is_blob)
 207                         goto bad_value;
 208                 goto okay;
 209
 210         case fs_param_is_fd: {
 211                 if (param->type != fs_value_is_file)
 212                         goto bad_value;
 213                 goto okay;
 214         }
 215
 216         case fs_param_is_blockdev:
 217         case fs_param_is_path:
 218                 goto okay;
 219         default:
 220                 BUG();
 221         }
 222
 223 maybe_okay:
 224         if (ret < 0)
 225                 goto bad_value;
 226 okay:
 227         return p->opt;
 228
 229 bad_value:
 230         return invalf(fc, "%s: Bad value for '%s'", desc->name, param->key);
 231 unknown_parameter:
 232         return -ENOPARAM;
 233 }
 234 EXPORT_SYMBOL(fs_parse);
 235
 236 /**
 237  * fs_lookup_param - Look up a path referred to by a parameter
 238  * @fc: The filesystem context to log errors through.
 239  * @param: The parameter.
 240  * @want_bdev: T if want a blockdev
 241  * @_path: The result of the lookup
 242  */
 243 int fs_lookup_param(struct fs_context *fc,
 244                     struct fs_parameter *param,
 245                     bool want_bdev,
 246                     struct path *_path)
 247 {
 248         struct filename *f;
 249         unsigned int flags = 0;
 250         bool put_f;
 251         int ret;
 252
 253         switch (param->type) {
 254         case fs_value_is_string:
 255                 f = getname_kernel(param->string);
 256                 if (IS_ERR(f))
 257                         return PTR_ERR(f);
 258                 put_f = true;
 259                 break;
 260         case fs_value_is_filename_empty:
 261                 flags = LOOKUP_EMPTY;
 262                 /* Fall through */
 263         case fs_value_is_filename:
 264                 f = param->name;
 265                 put_f = false;
 266                 break;
 267         default:
 268                 return invalf(fc, "%s: not usable as path", param->key);
 269         }
 270
 271         ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 272         if (ret < 0) {
 273                 errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
 274                 goto out;
 275         }
 276
 277         if (want_bdev &&
 278             !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
 279                 path_put(_path);
 280                 _path->dentry = NULL;
 281                 _path->mnt = NULL;
 282                 errorf(fc, "%s: Non-blockdev passed as '%s'",
 283                        param->key, f->name);
 284                 ret = -ENOTBLK;
 285         }
 286
 287 out:
 288         if (put_f)
 289                 putname(f);
 290         return ret;
 291 }
 292 EXPORT_SYMBOL(fs_lookup_param);
 293
 294 #ifdef CONFIG_VALIDATE_FS_PARSER
 295 /**
 296  * validate_constant_table - Validate a constant table
 297  * @name: Name to use in reporting
 298  * @tbl: The constant table to validate.
 299  * @tbl_size: The size of the table.
 300  * @low: The lowest permissible value.
 301  * @high: The highest permissible value.
 302  * @special: One special permissible value outside of the range.
 303  */
 304 bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 305                              int low, int high, int special)
 306 {
 307         size_t i;
 308         bool good = true;
 309
 310         if (tbl_size == 0) {
 311                 pr_warn("VALIDATE C-TBL: Empty\n");
 312                 return true;
 313         }
 314
 315         for (i = 0; i < tbl_size; i++) {
 316                 if (!tbl[i].name) {
 317                         pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
 318                         good = false;
 319                 } else if (i > 0 && tbl[i - 1].name) {
 320                         int c = strcmp(tbl[i-1].name, tbl[i].name);
 321
 322                         if (c == 0) {
 323                                 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
 324                                        i, tbl[i].name);
 325                                 good = false;
 326                         }
 327                         if (c > 0) {
 328                                 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
 329                                        i, tbl[i-1].name, tbl[i].name);
 330                                 good = false;
 331                         }
 332                 }
 333
 334                 if (tbl[i].value != special &&
 335                     (tbl[i].value < low || tbl[i].value > high)) {
 336                         pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
 337                                i, tbl[i].name, tbl[i].value, low, high);
 338                         good = false;
 339                 }
 340         }
 341
 342         return good;
 343 }
 344
 345 /**
 346  * fs_validate_description - Validate a parameter description
 347  * @desc: The parameter description to validate.
 348  */
 349 bool fs_validate_description(const struct fs_parameter_description *desc)
 350 {
 351         const struct fs_parameter_spec *param, *p2;
 352         const struct fs_parameter_enum *e;
 353         const char *name = desc->name;
 354         unsigned int nr_params = 0;
 355         bool good = true, enums = false;
 356
 357         pr_notice("*** VALIDATE %s ***\n", name);
 358
 359         if (!name[0]) {
 360                 pr_err("VALIDATE Parser: No name\n");
 361                 name = "Unknown";
 362                 good = false;
 363         }
 364
 365         if (desc->specs) {
 366                 for (param = desc->specs; param->name; param++) {
 367                         enum fs_parameter_type t = param->type;
 368
 369                         /* Check that the type is in range */
 370                         if (t == __fs_param_wasnt_defined ||
 371                             t >= nr__fs_parameter_type) {
 372                                 pr_err("VALIDATE %s: PARAM[%s] Bad type %u\n",
 373                                        name, param->name, t);
 374                                 good = false;
 375                         } else if (t == fs_param_is_enum) {
 376                                 enums = true;
 377                         }
 378
 379                         /* Check for duplicate parameter names */
 380                         for (p2 = desc->specs; p2 < param; p2++) {
 381                                 if (strcmp(param->name, p2->name) == 0) {
 382                                         pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
 383                                                name, param->name);
 384                                         good = false;
 385                                 }
 386                         }
 387                 }
 388
 389                 nr_params = param - desc->specs;
 390         }
 391
 392         if (desc->enums) {
 393                 if (!nr_params) {
 394                         pr_err("VALIDATE %s: Enum table but no parameters\n",
 395                                name);
 396                         good = false;
 397                         goto no_enums;
 398                 }
 399                 if (!enums) {
 400                         pr_err("VALIDATE %s: Enum table but no enum-type values\n",
 401                                name);
 402                         good = false;
 403                         goto no_enums;
 404                 }
 405
 406                 for (e = desc->enums; e->name[0]; e++) {
 407                         /* Check that all entries in the enum table have at
 408                          * least one parameter that uses them.
 409                          */
 410                         for (param = desc->specs; param->name; param++) {
 411                                 if (param->opt == e->opt &&
 412                                     param->type != fs_param_is_enum) {
 413                                         pr_err("VALIDATE %s: e[%tu] enum val for %s\n",
 414                                                name, e - desc->enums, param->name);
 415                                         good = false;
 416                                 }
 417                         }
 418                 }
 419
 420                 /* Check that all enum-type parameters have at least one enum
 421                  * value in the enum table.
 422                  */
 423                 for (param = desc->specs; param->name; param++) {
 424                         if (param->type != fs_param_is_enum)
 425                                 continue;
 426                         for (e = desc->enums; e->name[0]; e++)
 427                                 if (e->opt == param->opt)
 428                                         break;
 429                         if (!e->name[0]) {
 430                                 pr_err("VALIDATE %s: PARAM[%s] enum with no values\n",
 431                                        name, param->name);
 432                                 good = false;
 433                         }
 434                 }
 435         } else {
 436                 if (enums) {
 437                         pr_err("VALIDATE %s: enum-type values, but no enum table\n",
 438                                name);
 439                         good = false;
 440                         goto no_enums;
 441                 }
 442         }
 443
 444 no_enums:
 445         return good;
 446 }
 447 #endif /* CONFIG_VALIDATE_FS_PARSER */